ESPE Abstracts

The overall remission rate after 2 years of anti-thyroid drug treatment (ATD) in pediatric patients with autoimmune hyperthyroidism (AI) is 20-30%. The European Thyroid Association (ETA) recommends longer duration of ATD therapy in patients who have low likelihood of remission. Older age, female sex, ethnicity, small goiter, mild biochemical derangement at diagnosis, lower TSH receptor antibodies (TRAb) titer, history of other autoimmune conditions, duration of ATD treatment, are reported as factors associated with improved likelihood of remission following ATD. This retrospective study included 80 patients with AI ≤ 18 years treated in the Pediatric Endocrinology Center of the IRCCS San Raffaele in Milan from 2000 to 2021. Clinical manifestations, laboratory data, and follow-up records were collected for all patients. Children who achieved remission after a first cycle of methimazole were compared with those who had a relapse of disease to identify which variables were associated with relapse. Patients who suspended therapy were 48 (61%); 24 subjects (50%) relapsed and resumed therapy and the remaining 24 (50%) went into remission. A significant difference was found for I-II degree familiarity for autoimmune thyroid disease (AITD); only 3/48 (6.3%) patients in remission had a family history of AITD, while 11/48 (22.9%) patients who relapsed had a family history of AITD (p-value 0.024). Orbitopathy was found in 10/48 patients (21%); 8/10 (80%) patients relapsed after discontinuation of therapy (p-value 0.036). FT3/FT4 ratio at diagnosis resulted significantly higher in patients who relapsed (median of 0.465 vs 0.360 pmol/pmol, p value 0.001). Through the ROC test we identified a cut-off of 0.42 pmol/pmol which showed a sensitivity of 83% and a specificity of 66% to predict a relapse; on univariate analysis this cut-off increased the risk of relapse (p value <0.001, OR 12.1), and it proved to be and independent risk factor on multivariate analysis (p value 0.012, OR 7.18). Also for FT3/FT4 ratio before therapy withdrawal, a significant difference was found (median of 0.430 vs 0.330 pmol/pmol respectively, p value <0,001). In this case a FT3/FT4 ratio ≥ 0.38 pmol/pmol increased the risk of relapse (p value 0.003, OR 7.8). Another interesting data concerns the normalization time of FT3 after the start of methimazole (median of 60 vs 30 days respectively, p-value 0.038). FT3/FT4 ratio at diagnosis and before suspension of therapy, could be used as predictive factors of positive or negative disease outcome. These data require confirmation through prospective and multicenter studies.